A happiness expert shares the 10-second habit her family uses every day to improve their relationships

Don't make them more so by trying to adhere to vague principles like "be kinder" or "show more affection."

If you really want to get more out of your relationships, try setting concrete goals for yourself — i.e. you should be able to ask yourself, "Did I do X today?" with a simple yes or no.

At least, that's according to Gretchen Rubin, the bestselling author of multiple books on happiness and habit formation, including the 2012 book " Happier at Home."

Rubin visited the Business Insider office for a Facebook Live interview in April and shared the concrete strategy she and her family use to maintain positive relationships: warm greetings and farewells.

That is, every time someone comes or goes, everyone gives a sincere hello or goodbye.

"It's to really recognize that someone is coming or going," Rubin said. "It's really to look the person in the eye; say hello; have a little exchange; and to acknowledge the fact that they are coming or going."

Rubin said this habit works to strengthen relationships for a few reasons. As mentioned above, it's measurable. You either said hello to someone or you didn't.

What's more, it's hard to forget about it. You know exactly when you're supposed to make the connection — when someone enters or leaves a room. "It's not like, 'Do three good deeds throughout the day,' when you're like, 'Oh, I totally forgot," Rubin said.

Finally, warm greetings and farewells don't take much energy, money, or time — you're not, say, enrolling the entire family in a dance class.

Earlier in our interview, Rubin talked about the ways good relationships can make us happy — something both scientists and philosophers agree on. If you're trying to boost your happiness, your relationships are probably the first place you should look.

Rubin said that giving warm greetings and farewells have made a big difference in her household — but she added that you can use the same technique at work, with your colleagues.

"I am amazed at how much it creates a sense of connection and recognition," Rubin said. "And that's what we want from our relationships."